This invention relates to valve components having a resilient sealing surface, and in particular to a valve seat having a groove or step for mounting a resilient seal.
Conventional gate valves typically include a valve body, a valve seat assembly contained within the valve body, and an actuating assembly for moving the seat assembly to control the fluid flow through the body. Commonly, the valve seat is a generally cylindrical hollow component having a surface at one end adapted to mate with a portion of the valve body. Since the seat and valve body are typically perpendicularly oriented cylinders, their "intersection" is not planar, but rather eccentric or saddle-shaped. Conventionally, a resilient material is mounted onto the saddle-shaped surface of the valve seat, to assure a tight seal against the valve body. One known technique is to machine a groove or step in the valve seat surface, then mold vulcanized rubber of approximately 90 durometer to the groove or step.
The effectiveness and longevity of the valve are usually limited by the precision and durability of the valve seat seal. In time, the rubber deteriorates and the valve must be repaired. Conventionally, such repairs require replacing the entire valve seat, since it is impossible to replace, in the field, only the molded rubber. As is well known, proper molding of the rubber onto the metal seat requires careful surface preparation and controlled time and temperature conditions which are not normally available where gate valves are frequently used, e.g., oil and gas wells.
The limitations of presently known techniques for fabricating valve seats having resilient seals, and the inability to quickly repair deteriorated seals, have resulted in high costs for manufacturing and maintaining gate valves for use in oil and gas fields. Accordingly, there exists a great and long felt need for improvements to gate valve seats that would reduce the cost of manufacture and enable users to quickly and inexpensively replace worn resilient seals.